Adult-onset medulloblastoma presenting in the setting of untreated spina bifida: illustrative case

Given the abnormal posterior fossa development in patients with spina bifida and Chiari type II malformation, posterior fossa surgery requires a thorough understanding of the patient's venous sinus anatomy to achieve a maximal safe resection and prevent venous sinus injury or thrombosis. While the role of CSF diversion in adults with untreated spina bifida is unknown, the authors opted to proceed with postresection ventriculoperitoneal shunt placement given the persistent mass effect on the fourth ventricle from peritumoral swelling. Additional studies are needed to establish a molecular and/or genetic relationship between medulloblastoma and spinal dysraphism. https://thejns.org/doi/10.3171/CASE24897.